The effects of second hand smoke in indoor environments on non-smokers is an important question. Surveys of children with asthma suggest that more severe respiratory symptoms and poorer lung function tests occur if these children are exposed to smoke in their home environment. The purpose of this study will be to assess the changes in asthma as measured by lung function and the symptoms in children of those smoking parents who give up smoking; such children should have improved pulmonary function and reduced asthma symptoms. Up to 30 households with asthmatic children (male and female) between the ages of 6 - 18 years who have at least one smoking household member will be recruited for the study. Smokers will continue to smoke inside the home for the first three month period. For the second three month period smokers will be requested to completely give up smoking or at least stop smoking inside the home. During one month household smokers will participate in a smoking cessation program. The respiratory status of subjects will be monitored throughout the study by spirometry pre and post the administration of a bronchodilator and by methacholine challenge. Daily home peak flow measurements will be taken and an asthma diary kept for subjects. Subjects and smokers will be monitored for exposure to nicotine. Their saliva will be tested for continine for each three month study. The household environment will be monitored by air sampling devices for marker of environmental tobacco smoke. Baseline levels obtained during the smoking period will be used to verify compliance during the smoking cessation period.